01 - Dissolve yeast in warm milk with 1 teaspoon of sugar in a small bowl. Let stand for 5 minutes until foamy and activated.
02 - Combine flour, remaining sugar, and salt in a large bowl. Add melted butter, egg, and activated yeast mixture. Stir until incorporated, then knead for 5-8 minutes until smooth and elastic. Shape into a ball, cover, and refrigerate for 1 hour.
03 - Place cold butter between two sheets of parchment paper. Pound and roll into an even 6x6 inch square. Refrigerate until firm.
04 - On a floured surface, roll chilled dough into a 12x12 inch square. Position butter block in the center and fold dough edges over to completely encase the butter, pinching seams to seal.
05 - Roll dough into a 16x8 inch rectangle. Fold into thirds like a letter. Rotate 90 degrees, roll out again, and fold once more. Wrap and refrigerate for 30 minutes.
06 - Repeat rolling and folding process one additional time. Return dough to refrigerator for another 30 minutes chilling period.
07 - Roll dough into a 16x10 inch rectangle. Cut into 8 equal triangles. Starting from the wide end, roll each triangle toward the tip to form classic crescent shape.
08 - Arrange shaped croissants on parchment-lined tray, cover loosely, and let rise in a warm, draft-free area until puffy and doubled in size, approximately 1-2 hours.
09 - Preheat air fryer to 320°F. Brush risen croissants with beaten egg wash for golden finish.
10 - Place 2-4 croissants in air fryer basket without overcrowding. Air fry for 8-10 minutes until deep golden brown and fully baked. Repeat with remaining croissants.
11 - Allow croissants to cool briefly on wire rack before serving warm.